Eddie Howe's team have also been knocked out of the Champions League and Carabao Cup during December.

"We know we can do better," Trippier said on Amazon Prime.

"The standards we have set throughout the last 18 months, we have come away from them a little bit in the last few games."

Uncharacteristic errors in defeats at Everton, Tottenham and in the EFL Cup at Chelsea earlier this month have also placed added scrutiny on the England full-back, who captained the side against Forest in the absence of Jamaal Lascelles.

The 33-year-old, who has widely been held up as a symbol of the club's transformation under Eddie Howe, offered a candid assessment of his own current form, while saying he is determined to return to his best quickly.

"My standards have dropped and my own performances have been nowhere near recently," added Trippier, who withdrew from Three Lions squad in November for personal reasons.

"I won't shy away from it. I have had a lot of setbacks in my career and this is just another one where I need to keep going and keep believing. I have always got that belief to bounce back."

Added commitments taking their toll

Newcastle's loss to Forest came in their 10th fixture in 31 days, and both Trippier and Howe believe the punishing schedule and a crippling injury list should be factored into their recent struggles.

"It is a lot of games and being in Europe has been a challenge for the club," Trippier said. "The majority of the players are not used to playing in the Champions League and it's been a challenge for the team.

"We've had a lot of injuries, the lads have given everything and worked hard for each other, but we have to start the second half of the season strong.

"Teams always go through moments and we are going through one now, but football changes quickly and for sure this team will bounce back."

Meanwhile, Howe added: "The big thing for us is that we haven't been able to train [properly] in a long period of time and hopefully now we'll get some training-ground time.

"I don't think physically we're at our best. I think that's obvious and I think I would be lying if I said otherwise."

Newcastle will travel to Anfield, a venue where they last won in 1994, to face title challengers Liverpool in their next Premier League fixture on 1 January.